Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.33	7.551%	$141.2467	$141.25	$141.25	$141.20
Purchase #2	$158.42	13.219%	$179.3615	$179.36	$179.35	$179.40
Purchase #3	$231.82	7.338%	$248.831	$248.83	$248.85	$248.80
Purchase #4	$169.86	9.562%	$186.102	$186.10	$186.10	$186.10
Purchase #5	$128.75	9.759%	$141.3147	$141.31	$141.30	$141.30
Purchase #6	$125.65	5.577%	$132.6575	$132.66	$132.65	$132.70
Purchase #7	$140.79	12.856%	$158.89	$158.89	$158.90	$158.90
7 purchase totals =	$1,086.62		$1,188.4034	$1,188.40	$1,188.40	$1,188.40